This is always an interesting topic that is surprisingly polarizing.
It seems like there are 3 camps: 1. LOVE music on the boat, 2. Like music on the boat at times, 3. HATE music on a boat.
The most angry and vocal are almost always #3. Probably due to the super-loud and rude people found in certain areas. They have to vent somewhere! But I think there are a lot of #1 and #2 that don't want to incur the pent-up rage of the #3s, so they keep quiet.
Funny, but I posted this same question on TheHullTruth, a mostly saltwater boat community, and there were a few angry #3s that posted early, but then the majority were comparing what speakers and sound systems they were running. #1's and #2's.
But most from that forum are saltwater fishermen running bigger boats. If you run 20-120 miles in a day, a little music isn't such a bad thing. By comparison, sitting in a little tin boat in the middle of a lake isn't the place for pounding music.
It seems the lines are also drawn by age. My parents are in their 80's. They love 60's and 70's classic rock, just not too loud. On the pontoon, I played a little Zeppelin, Doors, and Pink Floyd at low volumes, and everyone was smiling and enjoying it.
We, in our 50's and 60's tend to like it a little louder, 80's and 90's rock, typically, with a little classic R&B/crossover music mixed in.
The kids, on the other hand tend to like hard-thumping, profanity-filled rap music and terrible-sounding heavy metal or country music. Stuff that makes me want to claw my eardrums out.
Everyone has different tastes. Fortunately, we have freedom to choose what WE like on OUR boats. If a boat passes by playing obnoxious music, just smile and wave and be glad they kept going.